In the petrochemical industry there has existed a need for a versatile flange gasket and heat exchanger gasket made of a non-asbestos material. Generally, the characteristics desired of a gasket for industrial applications include: continuous, fail-safe operation thereby avoiding potential damage to human health, plant equipment and the surrounding environment; fire resistance; resistance to temperature differentials across the diameter of the gasket; chemical resistance; field ruggedness; positive sealing even when the gasket is misaligned; positive sealing when the gasket material differs in thermal expansivity with respect to the surface to be sealed; environmentally safe, non-asbestos construction; operability at high pressures and temperatures; resiliency, springiness, memory, and structural integrity particularly during thermal cycling from high temperatures to low temperatures and vice versa, thermal shock, or other thermal excursions; low torque requirements for maintaining a positive seal at all operational or accidental temperatures and pressures to avoid subjecting the flanges (or other surface) and flange bolts to warpage and/or other damage; inhibited gasket creep or cold flow; crush resistance to enhance the potential for gasket reusability; minimized extrusion of the gasket coating; and reduced installation and maintenance time. A gasket designed with these characteristics in mind is described in U.S. Pat. No. 5,421,594 and includes a corrugated metal core member encapsulated with an expanded graphite.
Although expanded graphite encapsulated gaskets provide a wide variety of desirable characteristics, they are incompatible with certain applications in which graphite degradation results from a particular combination of chemicals, temperatures, pressures, and other operational conditions. For example, these gaskets cannot be used in the presence of strong oxidizing compounds (e.g., concentrated nitric acids, highly concentrated sulfuric acid, chromium (VI) and permanganate solutions, chloric acid, and molten alkaline and alkaline earth metals) to which graphite is not resistant.